Absolutely no idea how to resolve this NullPointerException

Yes, I've read this and this, but to no success. Here's what I'm trying to do:

I've created this application, which, after the user enters a number of seconds and presses a button, a service starts, which turns off the screen, starts a timer (based on the number of seconds inputted) and stops only when said timer ends. After stopping, the screen turns on and a TextView gets changed. Now, the idea is that, if the user turns on the screen before the timer ends, the service stops and the TextView doesn't get changed.

My issue comes when, after manually turning on the screen, if you enter the application and kill it, I receive the following error:

//TimerTask that will cause the run() runnable to happen.
TimerTask myTask = new TimerTask() {
public void run() { stopSelf(); }
};
//Timer that will make the runnable run.
Timer myTimer = new Timer();